This relates to integrated circuits, and more particularly, to integrated circuits with guard rings.
Integrated circuits include digital circuitry, analog circuitry, and/or other functional circuitry formed in a semiconductor substrate. Regions of circuitry are often surrounded by guard rings.
A guard ring is a structure that is used to block undesirable signals. In a typical scenario, an integrated circuit has internal circuitry that is coupled to external equipment through input-output pads. Noise can potentially leak from the external equipment through the pads onto the internal circuitry. A guard ring may be placed around the internal circuitry in this type of situation to isolate the internal circuitry from the noise. Guard rings can also be formed around noisy circuits to prevent noise from interfering with the operations of nearby circuits.
To ensure that noise is adequately suppressed, conventional guard rings generally have large widths. This can lead to fabrication challenges. For example, it can be difficult to satisfy polysilicon density requirements in integrated circuits with guard rings of large widths. The guard rings are generally devoid of polysilicon structures, which can lead to uneven surface profiles during chemical-mechanical polishing (CMP) operations.
It would therefore be desirable to be able to provide an improved guard ring that satisfies advanced fabrication requirements.